Zeitgeist parachain integration - unknown consensus engine.

[yornaath]

We at zeitgeist are trying to integrate substrate-connect(smoldot) into our frontend application layer using the extension, but running into the following errors:

[runtime-zeitgeist] Failed to decode header from sync service: Unknown consensus engine specified in a digest log: [110, 109, 98, 115]
[runtime-zeitgeist] Failed to download :code and :heappages of blocks 0xa800…4f96: Couldn't decode header: Unknown consensus engine specified in a digest log: [110, 109, 98, 115]

We are building of the purestake/substrate fork and using nimbus to implement our consensus layer, if we are using the same algorithm and format exactly as moonbeam is beyond my awareness atm, but maybe @sea212 have some more info that is relevant.

Ref
Frontend instantiation of Scprovider
Para chain spec
Runtime creation

[sea212]

We use Nimbus for parachain consensus and parachain-staking pallet for managing candidate sets, staking and determining the active set.

Current snapshot of the crate versions used:

nimbus-primitives = { branch = "moonbeam-polkadot-v0.9.19", default-features = false, git = "https://github.com/purestake/nimbus", optional = true }
pallet-author-inherent = { branch = "moonbeam-polkadot-v0.9.19", default-features = false, git = "https://github.com/purestake/nimbus", optional = true }
pallet-author-mapping = { rev = "78db06c0203f61b35059304f7194ed5c10dcfda8", default-features = false, git = "https://github.com/purestake/moonbeam", optional = true }
pallet-author-slot-filter = { branch = "moonbeam-polkadot-v0.9.19", default-features = false, git = "https://github.com/purestake/nimbus", optional = true }
parachain-staking = { rev = "78db06c0203f61b35059304f7194ed5c10dcfda8", default-features = false, git = "https://github.com/purestake/moonbeam", optional = true }

[sea212]

Related to #2139 (comment)

[tomaka]

So I believe (but could be wrong) that Nimbus is not really compatible with light clients.
Due to the fact that light clients don't execute blocks, they can't know whether a Nimbus block is valid or not.
The fact that anyone can generate a valid header (but not necessarily a valid body) violates many assumptions about DoS resilience.

However, that's problematic only for standalone chains/relay chains.
When it comes to parachains, the source of truth is the relay chain and thus we can ignore the consensus engine. It is already the case that smoldot ignores the consensus engine of parachains, and all that is needed to support Nimbus is being able to parse the headers.

It's unfortunately not necessarily as simple as allow parsing Nimbus headers. This is all a bit complicated, and I probably need to tweak the blocks verification code as well. I want to avoid fuck ups where blocks accidentally don't get verified and that kind of things.

[yornaath]

@tomaka is this something you want to work on and if so do you have a very rough eta on when it could be implemented? I could also have a look, but just learning some rust so the learning curve for something like this would be a bit steep ^^